Subgrades constructed from loess-a loose and porous material-demonstrate significant compressibility and collapsibility. To study these properties of loess subgrades, this article proposes a vertical vibration compaction method (VVCM) that provides a reliable simulation of field compaction and investigates the factors influencing the deformation characteristics of loess subgrade by VVCM-prepared specimens. The results show that the correlation between the compression modulus of loess samples prepared by VVCM and that of core samples obtained from the construction site is more than 85 %. In addition, the deformation resistance of the VVCM sample is better than that of the traditional quasistatic compaction method (QSCM) sample. Under the same compaction factor and water content, the compressive modulus of VVCM sample is at least 10 % higher and its collapsibility coefficient is 10 % lower than that of QSCM sample. With the increase in compaction factor, the compression modulus increases and the collapsibility coefficient decreases, indicating improved resistance to compressive deformation and reduced susceptibility to collapse in loess. With the increase in water content, the compression modulus and collapsibility coefficient decrease, reflecting greater compressibility and increased collapse resistance in loess.

Urban road disasters occur frequently in northwest China.Vehicle dynamic load is an important factor causing pavement cracking, dislocation and subgrade settlement deformation. The long-term dynamic load exerted by vehicles on the subgrade has caused harm to the normal operation of urban roads and the safety of residents ' travel. On this basis, this paper uses Abaqus numerical analysis software to establish a 3D solid model of the actual road structure system. The indoor shear strength of the actual roadbed soil is tested, and the dynamic response law and settlement deformation characteristics of the loess subgrade under different moisture content, dry density, and vehicle load conditions are examined. Results show that under the action of vehicle load, the vertical strain and vertical displacement of the loess subgrade have an attenuation trend from shallow to deep. The attenuation rate shows a shallow, fast, deep, and slow change mode. The cumulative settlement deformation of the subgrade loess shows a gradual growth trend with the accumulation of cyclic vibration, demonstrating the phenomenon of large deformation in the early stage and stable development in the later stage. The loess structure of the subgrade will become more dense and the strength will be improved after multiple cycle vibrations. Under the action of vehicle load, the sedimentation deformation of loess subgrade increases with the growth of moisture content and load, and decreases with the growth of dry density. The above phenomenon shows that the water content of the loess roadbed can be controlled to effectively reduce the incidence of road disasters such as roadbed deformation and settlement. The research in this paper can provide a reference for the disaster prevention and mitigation of urban roads in the northwest loess area in the future.